Apparatus and method to locate an object

ABSTRACT

Method and arrangement to locate an object with a predetermined number of marks, the arrangement comprising a light source, a sensor and a processor, by means of the following steps:—illuminating the object with the light source;—receiving an image of the object and generate image pixel data including image pixel locations and image pixel intensities for each image pixel location with said sensor;—receiving the image pixel data and storing them in a memory;—comparing said image pixel intensities with a predetermined threshold;—determining object position based on said comparing;—using a digital match mask that corresponds with said object with said marks;—finding a best match between said digital match mask and said object on said object position;—determining mark positions within said object position from said best match.

FIELD OF THE INVENTION

[0001] The present invention relates to an arrangement to locate anobject, comprising a light source to illuminate the object, a sensor toreceive an image of the object and to generate image pixel dataincluding image pixel locations and image pixel intensities for eachimage pixel location, a processor to receive the image pixel data and tostore them in a memory.

PRIOR ART

[0002] Such an arrangement is known from the prior art for a widevariety of applications.

SUMMARY OF THE INVENTION

[0003] It is an object of the invention to provide an arrangement thatis able to locate predetermined marks in the object with a highaccuracy.

[0004] To that end, the invention provides an arrangement to locate anobject with a predetermined number of marks, comprising a light sourceto illuminate the object, a sensor to receive an image of the object andto generate image pixel data including image pixel locations and imagepixel intensities for each image pixel location, a processor to receivethe image pixel data and to store them in a memory and use them toassess location and/or light-intensity and/or color of said objectand/or predetermined number of marks, the processor being arranged toperform the following functions:

[0005] comparing said image pixel intensities with a predeterminedthreshold;

[0006] determining object position based on said comparing

[0007] using a digital match mask that corresponds with said object withsaid marks;

[0008] finding a best match between said digital match mask and saidobject on said object position;

[0009] determining mark positions within said object position from saidbest match.

[0010] By using such a match mask and finding a best match between thematch mask and the object on the object position, a very accuratedetermination of the mark positions is possible. Preferably, the markpositions form together a matrix or part of a matrix of at least twomark positions, preferably at least four mark positions. With the term‘matrix’ is meant to be understood any casing suitable for holdingarrays of samples in the broad sense, either directly (for example aswells on a microtiter plate) or indirectly (for example as containerslike test tubes in a test tube rack). Suitable matrices may also bematrices that can be broken, cut or divided by other means into smallermatrices depending on the number of containers or wells that isrequired.

[0011] Preferably, the object is a holder or a holder with marks such ascontainers for holding test samples. In an embodiment, the arrangementis part of an apparatus for detecting residues possibly present in testsamples, as described and claimed in co-pending European patentapplication number 01203936.8 filed on the same day as the presentapplication. After the positions of the containers holding the testsamples are accurately determined with the arrangement according to thepresent invention, it is easier to detect possible residues bymeasurements on the test sample positions, e.g., by color changemeasurements, as will be further explained below. Optionally, theobject, viz. the holder and/or the containers for holding test samples,may contain additional marks that can be recognized by the processor bycomparison with pre-loaded data sets. Suitable examples of saidadditional marks are barcodes, bumps, figures, numbers, pits, rings,text, trademarks, and the like.

[0012] The present invention also relates to a method to be carried outby an arrangement to locate an object with a predetermined number ofmarks, the arrangement comprising a light source, a sensor and aprocessor, the method comprising the following functions:

[0013] illuminating the object with the light source;

[0014] receiving an image of the object and generate image pixel dataincluding image pixel locations and image pixel intensities for eachimage pixel location with said sensor;

[0015] receiving the image pixel data and storing them in a memory;

[0016] comparing said image pixel intensities with a predeterminedthreshold;

[0017] determining object position based on said comparing;

[0018] using a digital match mask that corresponds with said object withsaid marks;

[0019] finding a best match between said digital match mask and saidobject on said object position;

[0020] determining mark positions within said object position from saidbest match.

[0021] In another embodiment, the invention relates to a computerprogram product to be loaded by an arrangement to locate an object witha predetermined number of marks, the arrangement comprising a lightsource, a sensor and a processor, the computer program product, afterbeing loaded by said arrangement, providing said arrangement with thefollowing functions:

[0022] illuminating the object with the light source;

[0023] receiving an image of the object and generate image pixel dataincluding image pixel locations and image pixel intensities for eachimage pixel location with said sensor;

[0024] receiving the image pixel data and storing them in a memory;

[0025] comparing said image pixel intensities with a predeterminedthreshold;

[0026] determining object position based on said comparing;

[0027] using a digital match mask that corresponds with said object withsaid marks;

[0028] finding a best match between said digital match mask and saidobject on said object position;

[0029] determining mark positions within said object position from saidbest match.

[0030] Finally, the invention is also directed to a data carrierprovided with a computer program product as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention will be explained with reference to some drawings.The drawings are not intended to limit the scope of protection of thepresent invention but only to illustrate the invention. The inventionitself is only limited by the scope of the annexed claims.

[0032]FIG. 1 shows a block diagram of the arrangement that can be usedto carry out the present invention;

[0033]FIG. 2 shows some details of a scanner that can be used in thepresent invention;

[0034]FIG. 3a shows a microtiter plate comprising a plurality ofcontainers to contain samples to be investigated; FIG. 3b shows a testtube rack comprising a plurality of samples to be investigated;

[0035]FIG. 4 shows a flow diagram of a method to determine an objectlocation in accordance with the invention

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0036] In FIG. 1, an overview is given of an arrangement that can beused to carry out the method according to the invention. The arrangementcomprises a processor 1 for carrying out arithmetic operations.

[0037] The processor 1 is connected to a memory component or to aplurality of memory components, for example a hard disk 5, Read OnlyMemory (ROM) 7, Electrically Erasable Programmable Read Only Memory(EEPROM) 9, and Random Access Memory (RAM) 11. Not all of these memorytypes need necessarily be provided. Moreover, these memory componentsneed not be located physically close to the processor 1 but may belocated remote from the processor 1.

[0038] The processor 1 is also connected to means for inputtinginstructions, data etc. by a user, like a keyboard 13, and a mouse 15.Other input means, such as a touch screen, a track ball and/or a voiceconverter, known to persons skilled in the art may be provided too.

[0039] A reading unit 17 connected to the processor 1 is provided. Thereading unit 17 is arranged to read data from and possibly write data ona data carrier like a floppy disk 19 or a CDROM 21. Other data carriersmay be tapes, DVD, etc, as is known to persons skilled in the art.

[0040] The processor 1 may also be connected to a printer 23 forprinting output data on paper, as well as to a display 3, for instance,a monitor or LCD (Liquid Crystal Display) screen, or any other type ofdisplay known to persons skilled in the art.

[0041] The processor 1 may be connected to a communication network 27,for instance, the Public Switched Telephone Network (PSTN), a Local AreaNetwork (LAN), a Wide Area Network (WAN), etc. by means of I/O means 25.The processor 1 may be arranged to communicate with other communicationarrangements through the network 27.

[0042] The processor 1 may be implemented as stand alone system, or as aplurality of parallel operating processors each arranged to carry outsubtasks of a larger computer program, or as one or more main processorswith several sub processors. Remote processors communicating withprocessor 1 through the network 27 may even carry out parts of thefunctionality of the invention.

[0043] All connections may be physical connections, however, wirelessconnections are also included within the scope of the invention.

[0044] The processor 1 is also connected to a scanner 29, e.g., a HP6300C Scanjet. On top of the scanner one or more objects can be located.Photographic images of said objects may also be placed on top of thescanner. Alternatively, a device that can perform the same function asthe scanner 29 may replace the scanner 29. Such a device may be adigital photo or video camera, a web cam apparatus or the like. Saiddevices may be arranged in such a manner that images from the object tobe located can be conveniently collected. Preferably, the object isplaced in a position above the lens of said device, for instance byusing a mounting construction and/or a carrying area of transparentmaterial such as a glass plate. The distance between the lens of saiddevice and the object to be located is preferably less than one meter,more preferably less than 0.5 meter, most preferably less than 0.1meter.

[0045] By carrying out certain functionalities by a central processorthrough a WAN such as the Internet, additional advantages can berealized. In this way, all users will use the same and the latestsoftware versions, irrespective of their localization. Thus, the riskthat in some cases outdated software is used, is circumvented. Drawbacksof using outdated software are e.g. the fact that the latest legislativerequirements are not incorporated, corrections with regard to deviatingscanners 29 or objects are not incorporated, and results obtained bydifferent users cannot be uniformly interpreted. Any person ororganization, e.g. the manufacturer of the test systems or a regulatoryinstitute, may operate the central processor. Thus, an additionaladvantage is that the manufacturer of the test systems or the regulatoryinstitute can equip test systems with individual codes that are e.g.related to the production batch so that specifically tailored programson the central processor can be accessed using the code. Preferably,access to said central processor is achieved using the Internet by meansof personalized access code systems that are well known to the personskilled in the art. Alternatively, objects can be scanned orphotographed by a user and the digital or analogous image resulting fromthis scan or photograph can then be send in various ways, i.e. byelectronic mail, to the manufacturer of the test systems, a regulatoryinstitute or others for further processing such as calibration or thelike.

[0046] In accordance with the invention, the object has marks that canbe distinguished from the rest of the object. Preferably, the object isa test tube array or microtiter plate 31 (alternatively called“multiplate”) arranged to comprise test samples. In a preferredembodiment of the invention, these test samples are parts of a human oranimal body, or parts of plants or trees. Test samples also include meattissue fluid, milk, blood and eggs. Other examples are given below.

[0047]FIG. 2 shows some more details of a possible embodiment of thescanner 29. Others may be apparent to persons skilled in the art ofscanners. The invention is not restricted to one type of scanner andalso encompasses alternative devices that can perform the same functionas a scanner.

[0048] The scanner 29 comprises a transparent plate 35, e.g., made ofglass or plastic. On top of the transparent plate 35 one or more objectsare located. The objects shown are microtiter plates or test tube racks31 with containers 33 for containing samples to be tested.

[0049] Below the plate 35, a sensor 37 is located. The sensor 37 can bemoved by a driver (not shown), e.g., a motor, parallel to the plate tosense all objects on the plate 35. In order for the sensor to be able tosense the objects, a light source 43 is provided supported by asupporting member 45 that also supports the sensor 37. Thus, the lightsource 43 and the sensor 37 move together. The light source 43 may be anincandescent lamp or a gas discharge lamp. The sensor 37 may compriseCCD (Charge Coupled Device) elements. The sensor 37 may be of any othertype known to persons skilled in the art. It is not strictly necessarythat the light source 43 and the sensor 37 move together.

[0050] The sensor 37 is connected to a processor 39. The processor 39 isconnected to a memory 43. The memory 43 may be implemented in the sameway as the memories 5, 7, 9, 11 in FIG. 1, i.e., it may be a singlememory or may include several memories of different types.

[0051] The processor 39 is connected to an I/O (Input/Output) device 41that is arranged to communicate with processor 1 (FIG. 1).

[0052] Thus, the arrangement shown in FIGS. 1 and 2 comprises twoprocessors 1, 39. This is because scanner 29 is preferably a standardscanner that is commercially available. However, it will be evident to aperson skilled in the art that one can design a dedicated arrangementhaving only one processor performing all functions.

[0053]FIG. 3a shows a top view of an example of a microtiter plate 31with 96 containers 33 to contain samples to be tested. FIG. 3b shows abottom view of an example of a test tube rack 31 with 50 ampoules 33 tocontain samples to be tested. The microtiter plate and test tube rack 31may be made of plastic or any other suitable material known to personsskilled in the art.

[0054] Now, the operation of the arrangement shown in FIGS. 1, 2 and 3will be given with reference to FIG. 4. It is assumed that the object isa microtiter plate 31, but the person skilled in the art will understandthat other types of sample holding devices may be employed. Suitableexamples are test-tube racks containing test tubes designed in such afashion that the contents are at least visible from the side with whichthey are placed on the scanner.

[0055] An operator locates one or more microtiter plates 31 on the plate35. A standard microtiter plate 31 may comprise 96 containers (or“cups”) 33 arranged in 12 rows and 8 columns. The containers 33 arefilled with samples to be tested. The microtiter plate 31 may be suchthat it can be broken after the second, fourth, sixth, etc. row in orderto make smaller microtiter plates 31 with less containers, if desired.So, the microtiter plates on the plate 35 need not have the same sizes.The operator needs to inform the arrangement about the size data of themicrotiter plates 31 or the arrangement may be equipped with softwarethat enables automatic detection of the size data of the test arraybased on the present matrix. After the arrangement has started, step401, the arrangement waits for the operator to input these size data,step 403. The operator can input this size data with the keyboard 13 orthe mouse 15, or any other kind of input means, depending on theinterface offered to the operator via monitor 3. As outlined above, thearrangement may also start its own routine for determining the sizedata.

[0056] In step 405, the light source 43 is powered and moved togetherwith the sensor 37 parallel to the plate 35 such that images of allmicrotiter plates 31 are sensed with the sensor 37. The images arereceived by the processor 39, step 407. The images may be stored inmemory 43 in the form of image pixel data including image pixel locationand image pixel intensity for each pixel in the image. Then, the imagesare sent to processor 1 that stores these same data in memory 5, 7, 9,and 11 and creates a cumulative histogram of all pixel intensities, step409.

[0057] In step 411, the processor 411 determines a sum of surfaces ofexpected microtiter plates 31. This can be done by using the informationregarding the sizes of the microtiter plates 31 as received from theoperator in step 403 and the cumulative histogram of step 409.

[0058] In step 413, a threshold value is determined. In an embodiment,the images of the microtiter plates 31 are lighter than the images ofthe background of these microtiter plates 31. Therefore, the microtiterplates 31 may be recognized by their higher image pixel intensity valuescompared with lower image pixel intensity values for the background. Instep 415, image pixels having an intensity value below the threshold,which correspond to the background, are removed from further processing.Of course, instead of having a much darker background one can use a muchlighter background when the microtiter plates would be darker. Then, allimage pixels with an intensity value above the threshold would beremoved.

[0059] Then, optionally, one or more of the following operations isperformed on the remaining data:

[0060] a propagation operation in order to close “holes” in the image(step 417);

[0061] one or more, e.g. 5 times, erosion operations to delete smallinterference/noise objects (step 419);

[0062] one or more, e.g. 5 times, dilation operations to repair erosionsfor larger objects (step 421).

[0063] Such operations are known to persons skilled in the art.

[0064] In step 423, the locations of the microtiter plates 31 aredetermined. This corresponds with finding the external boarders of theimage pixel locations having an image pixel intensity above thethreshold.

[0065] The result of step 423 can be checked. In step 425, the processor1 counts the number of all image pixels falling within these externalboarders and compares this number with a number of image pixels to beexpected based on the information received from the operator in step403. If these numbers are equal within a certain error margin, then, theprocessor 1 can be sure that the microtiter plates 31 are foundcorrectly.

[0066] Using known image processing techniques, the area of eachmicrotiter plate image is rotated, step 427, such that the images haveboarders parallel to a predetermined X-Y plane.

[0067] In step 429, for each of the microtiter plates 31 a match mask isgenerated. Each match mask is a simulated image of a microtiter plate 31and comprises as many containers 33 as there are in the correspondingreal microtiter plate 31. The information as to the number of containers33 per microtiter plates 31 is derived from the information received instep 403. The relative positions of the containers 33 in the match masksto the boarders thereof is then also known to the arrangement.

[0068] In step 431, for each match mask and its corresponding microtiterplate 31, a best match is determined between said match masks and therotated images by virtually shifting said match masks in the X-Y plane.Preferably, a cross correlation operation is used. After these bestmatches are found, the positions of the containers 33 in the microtiterplates can be determined, step 433, using container position data fromthe match masks. Since the containers 33 always have a fixed distance tothe boarders of the microtiter plates 31, there is no need to derive thepositions of the containers 33 separately from the images as sensed bysensor 37, which would be much more cumbersome and susceptible toerrors.

[0069] Instead of rotating the images of the microtiter plates 31, thearrangement can be programmed to rotate and shift the match masks tofind the best match between the match masks and the images of themicrotiter plates 31. In general, it does not matter what kind of axessystem is used and what kinds of operations are performed to find thebest matches.

[0070] After having accurately determined the positions of thecontainers 33 in this way, further measurements as to the content of thecontainers can be made, as explained in co-pending European patentapplication number 01203936.8 “Apparatus and method for detectingundesired residues in a sample” of the same applicant.

[0071] The invention is not limited to using light of a visiblespectrum. It is emphasized that the arrangement may also give goodresults using infrared or ultraviolet light.

1. An arrangement to locate an object with a predetermined number of marks, comprising a light source to illuminate the object, a sensor to receive an image of the object and to generate image pixel data, the image pixel data comprising image pixel locations and image pixel intensities for each image pixel location, a processor to receive the image pixel data and to store the image pixel data in a memory, the processor being arranged to perform functions comprising comparing said image pixel intensities with a predetermined threshold; determining object position based on said comparing; using a digital match mask that corresponds with said object with said marks; finding a best match between said digital match mask and said object on said object position; and determining mark positions within said object position from said best match.
 2. The arrangement of claim 1, wherein the object is a holder and the marks are containers for holding test samples.
 3. The arrangement of claim 2, wherein the test samples comprise at least one of the set of samples selected from the group consisting of parts of an animal body, parts of a human body, and parts of plants and trees.
 4. The arrangement of claim 1, wherein the sensor comprises a series of CCD elements.
 5. The arrangement of claim 1, wherein the processor is arranged to determine mark positions in a plurality of objects.
 6. The arrangement of claim 1, wherein the processor is arranged to perform a propagation operation after said comparing said image pixel intensities with said predetermined threshold.
 7. The arrangement of claim 6, wherein the processor is arranged to perform at least one erosion operation after said propagation operation.
 8. The arrangement of claim 7, wherein the processor is arranged to perform at least one dilation operation after said erosion operation.
 9. The arrangement of claim 1, wherein said light source and said sensor are part of a scanner.
 10. A method to be carried out by an arrangement to locate an object with a predetermined number of marks, the arrangement comprising a light source, a sensor and a processor, the method comprising the functions of illuminating the object with the light source; receiving an image of the object and generating image pixel data, the image pixel data comprising image pixel locations and image pixel intensities for each image pixel location with said sensor; receiving the image pixel data and storing the image pixel data in a memory; comparing said image pixel intensities with a predetermined threshold; determining object position based on said comparing; using a digital match mask that corresponds with said object with said marks; finding a best match between said digital match mask and said object on said object position; and determining mark positions within said object position from said best match.
 11. A computer program product to be loaded by an arrangement to locate an object with a predetermined number of marks, the arrangement comprising a light source, a sensor and a processor, the computer program product, after being loaded by said arrangement, providing said arrangement with functions comprising illuminating the object with the light source; receiving an image of the object and gestate generating image pixel data, the image pixel data comprising image pixel locations and image pixel intensities for each image pixel location with said sensor; receiving the image pixel data and storing the image pixel data in a memory; comparing said image pixel intensities with a predetermined threshold; determining object position based on said comparing; using a digital match mask that corresponds with said object with said marks; finding a best match between said digital match mask and said object on said object position; and determining mark positions within said object position from said best match.
 12. A data carrier provided with a computer program product according to claim
 11. 